1. Field of the Invention
This invention relates to isolation and improvement of impact modifier polymer powders and to blends of thermoplastic matrix polymers with such impact modifier polymer powders.
2. Description of the Prior Art
Isolation of impact modifier polymers while simultaneously adding finely divided inorganic materials is known. Ferry et al U.S. Pat. No. 3,985,703 and Jones et al U.S. Pat. No. 3,985,704 suggest use of inert particulate material being blown into a spray dryer during isolation of impact modifier polymers.
Matschke et al U.S. Pat. No. 3,883,489 suggest finely divided silica, aluminum silicates or calcium carbonate having an average particle size of from 0.01 to 0.5 micron as anti-caking agents being added during spray drying of vinyl acetate-ethylene copolymer dispersable powders for use as glues, adhesives and paints, and as binding agent in plastic mortars. The powders have improved dispersability and improved storage life.
Except for one patent, Heichle et al U.S. Pat. No. 3,996,173, no one has suggested the use of stearate coated calcium carbonate in combination with an impact modifier polymer. However, Heichle et al only teach a synergistic impact strength improvement effect in a ternary composition of PVC, impact modifier polymer, and stearate-coated calcium carbonate. Neither Heichle et al nor anyone else teach isolation of the impact modifier using the stearate coated calcium carbonate, or the resultant binary blends.